Sexual dimorphism of insular cortex function in persistent alcohol drinking despite aversion in mice

Abstract

ABSTRACTBACKGROUNDOne major hallmark of alcohol use disorder (AUD) is the persistence of alcohol drinking despite negative consequences. Among the indicators of AUD vulnerability, binge drinking is a strong risk factor. Although the lifetime prevalence of binge and AUD has been historically higher in men than women, this gap dramatically narrowed in the last decade. Additionally, sex differences in AUD and binge drinking have been shown in clinical and preclinical studies, respectively. The insular cortex plays an important role in AUD, and the anterior (aIC) and posterior (pIC) divisions have dimorphic functions. However, the contributions of the aIC and pIC sections in alcohol binge drinking and alcohol persistent drinking despite aversion, as well as the sexual dimorphism of these contributions, remained to be uncovered.METHODSFirst, by combining the drinking in the dark model with chemogenetics, we studied the causal role of aIC and pIC excitatory neurons in binge and persistent ethanol drinking in C57BL6/J male (n=49) and female (n=49) mice. Second, using calcium fiber photometry, we investigated pIC neuronal activity in both sexes (male n=14, female n=11) during both binge and persistent ethanol drinking.RESULTSWe identified a higher binge and persistent ethanol consumption in females compared to males. Chemogenetic inhibition of aIC glutamatergic neurons reduced bitter solutions intake independently of the solvent (ethanol or water), in both sexes. In contrast, inhibition of pIC glutamatergic neurons exclusively reduced persistent ethanol drinking in female mice. Finally, using fiber photometry recordings, we uncovered that pIC glutamatergic neuron activity was selectivity increased during ethanol persistent drinking in female mice.CONCLUSIONSThese findings suggest a sex-dependent function of the pIC in persistent ethanol drinking, providing a starting point in our understanding of the insular cortex function in the neurobiology of AUD in both sexes.